Sprinkle the chicken with salt and pepper. Heat a large stainless steel skillet over medium-high heat. Add the oil and sear the chicken for 5 minutes. Turn the chicken over, reduce the heat to medium and cook until done, about 5 more minutes. Remove the chicken from the pan and let stand 5 minutes.
In the pan that was used to cook the chicken, deglaze with the chicken stock and bring to a simmer. Then lower the heat so that the stock just stays hot.
Meanwhile, in a separate heavy-bottomed saucepan, melt the clarified butter over a medium heat until it becomes frothy. Take care not to let it turn brown. With a wooden spoon, stir the flour into the melted butter a little bit at a time until it is fully incorporated, giving you a pale yellow paste called a roux. Heat the roux for another few minutes or so, until it has turned a light blonde color. This helps cook off the raw flour flavor. But since this is a white sauce, you don't want to let the roux get too dark.
Using a wire whisk, slowly add the hot chicken stock to the roux, whisking vigorously to make sure it's free of lumps. Simmer until the total volume has reduced by about one-third, stirring frequently to make sure the sauce doesn't scorch at the bottom of the pan, about 30 minutes. Use a ladle to skim off any impurities that rise to the surface.